Thermo-oxidative stability studies on some new generation API group II and III base oils

Due to the increasing demand for highly saturated (group II and III) base oils for use in specialty lubricant application, it is necessary to obtain a clear picture of the base oil molecular distribution. These oils are more stable to oxidation and exhibit superior performance-based characteristics as compared with group I type base oils. With the aromatic content reaching a minimum value, saturated molecules control most of the physical properties in these oils. Molecular structure based characterization developed for conventionally refined base oils will be inadequate to address all the structural diversities of these base fluids. In this study, results from thin film micro oxidation (TFMO) and pressure differential scanning calorimetry (PDSC) were discussed in terms of the quantitative C-13 NMR (inverse gated, CSE, GASPE) data. Correlations obtained with physical properties (e.g. viscosity), oxidation (evaporation, insoluble deposit) and structural data indicate the significance of base oil's saturate hydrocarbon structures in influencing most of the performance properties. (C) 2001 Elsevier Science Ltd. All rights reserved.